Surgical stapling apparatus with firing lockout mechanism

ABSTRACT

A surgical stapling device is provided which includes a first jaw supporting an anvil assembly and a second jaw supporting a cartridge assembly. The cartridge assembly supports a firing lockout assembly which includes a latch member having a blocking portion. The latch member is movable between a first position and a second position. In the first position, the blocking portion of the latch member is aligned with the stop surface of the drive member to prevent advancement of the drive assembly beyond an initial advanced position within the tool assembly and in the second position, the blocking member is misaligned with the stop surface of the drive member to permit subsequent advancement of the drive assembly within the tool assembly. In the retracted position of the drive assembly subsequent to firing of the surgical stapling device, the latch member is in the first position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 16/814,050, filed Mar. 10, 2020, the entire content of which is hereby incorporated by reference herein.

FIELD

This disclosure relates to surgical stapling apparatus. More particularly, this disclosure relates to surgical stapling apparatus having a firing lockout mechanism.

BACKGROUND

Surgical stapling apparatus for stapling tissue are well known in the art and typically include a handle assembly, a body portion extending distally from the handle assembly, and a tool assembly supported on a distal end of the body portion. The tool assembly includes first and second jaws which are movable in relation to each other between open or unapproximated and approximated positions. The first jaw supports an anvil assembly and the second jaw supports a cartridge which houses a plurality of staples. The cartridge can also include a knife for severing tissue. In known apparatus, a fired or spent cartridge can be replaced with an unfired or fresh cartridge to facilitate reuse of the surgical stapling apparatus.

In order to prevent refiring of the surgical stapling apparatus with a spent cartridge, or to prevent firing of a surgical stapling apparatus which does not include a cartridge, it is known to provide a lockout mechanism which prevents advancement of a drive member of the stapling apparatus. Although known lockout mechanisms are effective to prevent firing of a surgical stapling apparatus which includes a spent cartridge or does not include a cartridge, an improved, reliable lockout mechanism is desired.

SUMMARY

A surgical stapling device includes a body portion defining a longitudinal axis having a proximal end and a distal end, a tool assembly supported on the distal end of the body portion, a drive assembly movably supported within the tool assembly from a retracted position to an initial advanced position to move the tool assembly from the open position to the approximated position, and a firing lockout assembly. The tool assembly includes an anvil assembly, a channel member pivotally supported relative to the anvil assembly, and a cartridge assembly releasable disposed within the channel member. The tool assembly is movable from an open position to an approximated position. The cartridge assembly supports a plurality of staples and includes an actuation sled movable between a retracted position and an advanced position to eject the plurality of staples from the cartridge assembly. The drive assembly has a stop surface. The firing lockout assembly includes a latch member having a blocking portion. The latch member is pivotally supported within the tool assembly and is movable from a first position to a second position. In the first position, the blocking member of the latch member is aligned with the stop surface of the drive member to prevent advancement of the drive member within the tool assembly beyond the initial advanced position, and in the second position, the blocking member is misaligned with the stop surface of the drive member to permit advancement of the drive member within the tool assembly beyond the initial advanced position. The actuation sled is positioned to retain the latch member in its second position when the actuation sled is in its retracted position and the tool assembly is in the approximated position.

In certain aspects of the disclosure, the actuation sled is positioned within the cartridge assembly to be engaged by the drive assembly subsequent to the drive assembly moving to the initial advanced position. Further advancement of the drive assembly may effect movement of the actuation sled from the retracted position to the advanced position upon movement of the drive member from the initial advanced position to a subsequent advanced position. The firing lockout assembly may further include a biasing member positioned to urge the latch member towards the first position.

In some aspects of the disclosure, the actuation sled includes an engagement feature, that engages the latch member to move the latch member from the first position to the second position when tool assembly is moved to the approximated position and the actuation sled is in the retracted position. The latch member may include first and second legs extending distally from the blocking portion. Each of the first and second legs may support a pivot member.

The latch member may include an extension extending from one of the first and second legs. The extension may engage the engagement feature to move the latch member to the second position when the tool assembly is moved to the closed position. Movement of the drive assembly beyond the initial advanced position may move the actuation sled from the retracted position to the advanced position to eject the plurality of staples from the cartridge assembly.

In aspects of the disclosure, the drive assembly includes a body and a clamping member including an upper flange and a lower flange interconnected by a vertical strut. The clamping member may be positioned to engage the actuation sled to move the actuation sled distally within the cartridge assembly as the drive assembly moves from its retracted position towards a fully advanced position. The body of the drive assembly includes the stop surface. The body of the drive assembly may include a guide surface for retaining the latch member in the second position. The anvil assembly may define a first cam surface and the cartridge assembly may define a second cam surface. The upper and lower flanges of the clamping member of the drive assembly may engage the first and second cam surfaces as the drive assembly moves from its retracted position to its initial advanced position to move the tool assembly to the approximated position.

In certain aspects of the disclosure, the blocking member of the latch member is positioned to engage a bottom surface of the body of the drive assembly as the drive assembly is moved from its initial advanced position towards its fully advanced position to retain the latch member in the second position. The actuation sled may be in abutting relationship with the clamping member of the drive assembly such that upon movement of the drive assembly from the advanced position back to the retracted position, the actuation sled remains in its advanced position.

Another surgical stapling device includes a body portion defining a longitudinal axis having a proximal end and a distal end, a tool assembly supported on the distal end of the body portion, a drive assembly movably supported within the tool assembly from a retracted position to an initial advanced position to move the tool assembly from the open position to the approximated position, the drive assembly having a stop surface, and a firing lockout assembly. The tool assembly includes an anvil assembly, a channel member pivotally supported relative to the anvil assembly, and a cartridge assembly releasable disposed within the channel member. The tool assembly is movable from an open position to an approximated position. The cartridge assembly supports a plurality of staples and includes an actuation sled movable between a retracted position and an advanced position to eject the plurality of staples from the cartridge assembly. The firing lockout assembly includes a latch member and a biasing member. The latch member has a blocking portion and is pivotally supported within the tool assembly between a first position to a second position. The biasing member is configured to urge the latch member to the first position. In the first position, the blocking member of the latch member is aligned with the stop surface of the drive member to prevent advancement of the drive member within the tool assembly beyond the initial advanced position. In the second position, the blocking member is misaligned with the stop surface of the drive member to permit advancement of the drive member within the tool assembly beyond the initial advanced position. The actuation sled is positioned to retain the latch member in its second position when the actuation sled is in its retracted position and the tool assembly is in the approximated position.

In certain aspects of the disclosure, the actuation sled is positioned within the cartridge assembly to be engaged by the drive assembly subsequent to the drive assembly moving to the initial advanced position. Further advancement of the drive assembly may effect movement of the actuation sled from the retracted position to the advanced position upon movement of the drive member from the initial advanced position to a subsequent advanced position.

In some aspects of the disclosure, the actuation sled includes an engagement feature, that engages the latch member to move the latch member from the first position to the second position when tool assembly is moved to the approximated position and the actuation sled is in the retracted position. The latch member may include first and second legs extending distally from the blocking portion. Each of the first and second legs may support a pivot member. The latch member may include an extension extending from one of the first and second legs. The extension may engage the engagement feature to move the latch member to the second position when the tool assembly is moved to the closed position.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the disclosure are described herein with reference to the drawings, wherein:

FIG. 1 is a side, perspective view of various aspects of the disclosed surgical stapling apparatus including a loading unit having a tool assembly in an open position;

FIG. 2 is a side, perspective view of the loading unit shown in FIG. 1, with an anvil assembly of the tool assembly shown in phantom;

FIG. 3 is an enlarged, side perspective view of the indicated area of detail shown in FIG. 2;

FIG. 4 is a side perspective view with parts separated of the loading unit shown in FIG. 2;

FIG. 5 is an enlarged, side perspective view of the indicated area of detail shown in FIG. 4;

FIG. 6 is a side, cross-sectional view taken along section line 6-6 shown in FIG. 3, with the tool assembly in the open position and a latch member of a lockout assembly in a first or locked position prior to firing of the surgical stapling apparatus;

FIG. 7 is an enlarged, side perspective view of the indicated area of detail shown in FIG. 6;

FIG. 8 is the side, cross-sectional view taken along section line 6-6 shown in FIG. 3, with the tool assembly in a closed position and the latch member in a first unlocked position prior to firing of the surgical stapling apparatus;

FIG. 9 is an enlarged, side perspective view of the indicated area of detail shown in FIG. 8;

FIG. 10 is the enlarged, side perspective view of FIG. 9 with the loading unit in a first partially fired condition and the latch member in a second unlocked position;

FIG. 11 is the enlarged, side perspective view of FIG. 10, with the loading unit in a second partially fired condition and the latch member in a third unlocked position; and

FIG. 12 is the enlarged, side perspective view of FIG. 11, with the loading unit in a post-fired condition and the latch member in the locked position.

DETAILED DESCRIPTION

The disclosed surgical stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that the disclosed aspects of the disclosure are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure in virtually any appropriately detailed structure. In addition, directional terms such as front, rear, upper, lower, top, bottom, distal, proximal, and similar terms are used to assist in understanding the description and are not intended to limit the disclosure.

In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician. In addition, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel.

The disclosed surgical stapling device includes a firing lockout assembly configured to prevent firing of the surgical stapling device when the surgical stapling device is not loaded or loaded with a spent cartridge assembly.

FIG. 1 illustrates a surgical stapling device according to exemplary aspects of the disclosure, shown generally as stapling device 10. The stapling device 10 includes a powered handle assembly 20, an adapter assembly 30 releasably secured to the powered handle assembly 20, and a loading unit 100 releasably secured to the adapter assembly 30. Although shown as individual or separable components, it is envisioned that any or all of the powered handle assembly 20, adapter assembly 30, and loading unit 100 may be integrally formed.

FIGS. 2-4 illustrate the loading unit 100 of the surgical stapling device 10 (FIG. 1) including a body portion 102 and a tool assembly 104 pivotally secured to the body portion 102. The tool assembly 104 includes a jaw assembly 106 including an anvil assembly 114, a channel member 118, and a cartridge assembly 116 that is received within the channel member 118. The anvil assembly 114 and cartridge assembly 116 are pivotable relative to each other between an open position (FIG. 2) and an approximated or clamped position (FIG. 8). A mounting assembly 120 pivotally couples the proximal body portion 102 of the loading unit 100 and the tool assembly 104. A drive assembly 130 (FIG. 4) which includes a dynamic clamping member 132 (FIG. 3) extends from the body portion 102 of the loading unit 100, through the mounting assembly 120 into the tool assembly 104. As will be described below, a firing lockout assembly 140 is supported within the tool assembly 104 to prevent the drive assembly 130 from being advanced beyond an initial advanced position in the absence of an unfired cartridge assembly 116 received within the channel member 118 of the jaw assembly 106.

The loading unit 100 is substantially as described in U.S. Pat. No. 9,016,539 (“the '539 patent”). Accordingly, the components of the loading unit 100 which are common to that which is disclosed in the '539 patent will only be described herein to the extent necessary to fully disclose the aspects of the firing lockout assembly 140 and its method of operation.

The anvil assembly 114 of the jaw assembly 106 includes an anvil body 150 and an anvil plate 152. The anvil plate 152 is secured to the underside of the anvil body 150 to define a channel 151 (FIG. 7) for receiving a portion of the dynamic clamping member 132 of the drive assembly 130 of the loading unit 100. The anvil plate 152 defines plurality of staple receiving depressions (not shown).

The cartridge assembly 116 of the jaw assembly 106 includes a cartridge body 156, a plurality of staples “5”, and a staple firing assembly 160 that includes an actuation sled 162 and a plurality of pusher members 164. The cartridge assembly 116 is releasably supported in the channel member 118. The cartridge body 156 is secured to the channel member 118 with a snap-fit connection. Other forms of connection are contemplated and may be used in place of the snap-fit connection, or in addition thereto. The channel member 118 is pivotally secured to the anvil body 150. The cartridge body 156 defines a plurality of laterally spaced staple retention slots 153 which are positioned in alignment with the staple receiving depressions (not shown) in the anvil plate 152 of the anvil assembly 114. Each slot 153 is configured to receive a fastener or staple “S” and a pusher 164. The actuation sled 162 is positioned within the cartridge body 156 of the cartridge assembly 116 and is configured to pass longitudinally through the cartridge body 156 into engagement with the pushers 164 to sequentially eject the staples “S” from the cartridge body 156.

The mounting assembly 120 includes an upper mounting member 170 (FIG. 4) and a lower mounting member 172 secured to the tool assembly 104. First and second coupling members 176, 178 pivotally secure the upper and lower mounting members 170, 172 to the proximal body portion 102 of the loading unit 100. The body portion 102 of the loading unit 100 includes upper and lower housing halves 180, 182 which are contained within an outer sleeve 184 (FIG. 2). The upper and lower housing halves 180, 182 (FIG. 4) define a channel 181 for slidably receiving the drive assembly 130.

The drive assembly 130 includes the dynamic clamping member 132 and a body 134. In certain aspects of the disclosure, the body 134 of the drive assembly 130 is formed from a plurality of stacked sheets that are formed of a resilient or flexible material, e.g., stainless steel. The dynamic clamping member 132 includes an upper flange 136 a, a lower flange 136 b, and a vertical strut 138 interconnecting the upper flange 136 a and the lower flange 136 b. A knife 138 a is supported on or formed into the vertical strut 138 of the dynamic clamping member 132. The upper flange 136 a is positioned to be slidably received within the channel 151 (FIG. 7) of the anvil assembly 114 and the lower flange 136 b is positioned to be slidably positioned along an outer surface 118 a (FIG. 6) of the channel member 118.

The distal portion of the body 134 of the drive assembly 130 supports the dynamic clamping member 132 of the drive assembly 130 and includes a stop surface 133 that is configured for engagement with the firing lockout assembly 140 when no cartridge assembly or a spent cartridge assembly 116 is loaded into the channel assembly 118 of the loading unit 100. The drive assembly 130 may further include a guide surface 135 to retain the firing lockout assembly 140 in its unlocked position as the dynamic clamping member 132 is advanced through the cartridge assembly 116.

When the stapling device 10 is operated, distal movement of the drive assembly 130 to the initial advanced position (FIG. 8) advances the upper flange 136 a of the dynamic clamping member 132 of the drive assembly 130 into a cam surface 153 (FIG. 7) formed on the anvil plate 152 and advances the lower flange 136 b of the dynamic clamping member 132 of the drive assembly 130 into engagement with a cam surface 131 formed on the channel member 118 of the jaw assembly 106 to pivot the cartridge assembly 116 from the open position towards the anvil assembly 114 to the approximated position (FIG. 8). Continued advancement of the drive assembly 130 beyond the initial advanced position progressively maintains a minimum tissue gap adjacent the dynamic clamping member 132 of the drive assembly 130 as the dynamic clamping member 132 moves through the jaw assembly 106.

FIG. 5 illustrates the proximal end of the channel member 118 of the jaw assembly 106, the firing lockout assembly 140, and the actuation sled 162 of the stapling assembly 160. The actuation sled 162 of the cartridge assembly 116 is disposed within the cartridge body 156 at a position distal of the dynamic clamping member 132 of the drive assembly 130. The actuation sled 162 includes a plurality of cam surfaces 165 (FIG. 5) that engage the pushers 164 (FIG. 4) within the cartridge body 156 to eject the staples “S” from the cartridge body 156 when the actuation sled 162 is advanced through the jaw assembly 106. A proximal end of the actuation sled 162 includes an engagement feature 162 a (FIG. 5).

The firing lockout assembly 140 of the loading unit 100 includes a latch member 200 and a biasing member 230, e.g., a leaf spring. The latch member 200 is pivotally supported on a proximal portion of the channel member 118 of the jaw assembly 106. The latch member 200 includes a U-shaped body having a base or blocking portion 202 and first and second legs 204, 206 extending distally from the base 202. The blocking portion 202 includes a proximal surface 202 a. In the absence of the actuation sled 162 of the stapling assembly 160, the proximal surface 202 a of the blocking portion 202 engages the stop surface 133 of the drive assembly 130 to prevent advancement of the drive assembly 130 beyond its initial advanced position (FIG. 8) The latch member 200 includes a pivot member 208 that extends outwardly from each of the first and second legs 204, 206 for pivotally securing the latch member 200 relative to the channel member 118. The latch member 200 is pivotal from a first or locked position (FIG. 7) wherein the blocking portion 202 is aligned with the stop surface 133 of the drive assembly 130 to prevent advancement of the drive assembly 130 within the tool assembly 104 and a second or unlocked position (FIG. 9) wherein the blocking portion 202 is misaligned with the stop surface 133 of the drive assembly 130 to permit advancement of the drive assembly 130 within the tool assembly 104 beyond its initial advanced position.

The latch member 200 includes an extension 210 extending distally from a distal portion of the first leg 204. The extension 210 engages an engagement feature 162 a of the actuation sled 162 when a pre-fired cartridge assembly 116 is loaded within the channel member 118 of the jaw assembly 106 of the loading unit 100. When the extension 210 is in engagement with the engagement feature 162 a of the actuation sled 162, pivoting of the jaw assembly 106 to the approximated position through advancement of the drive assembly 130 to its initial advanced position causes the latch member 200 to pivot to its second or unlocked position, thereby moving the blocking portion 202 of the latch member 200 out of alignment with the stop surface 133 of the drive assembly 130. When the blocking portion 202 of the latch member 200 is misaligned with the stop surface 133, i.e., the latch member 200 is in the unlocked position, the drive assembly 130 may be advanced through the cartridge assembly 116. The biasing member 230, urges the latch member 200 towards the first or locked position to engage the latch member 200 with the stop surface 133 of the drive assembly 130 in the absence of the actuation sled 162. The actuation sled 162 is absent when a cartridge assembly 116 is not received within the channel member 118 of the jaw assembly 106, or when a spent or previously fired cartridge assembly 116 is loaded within the channel member 118.

FIGS. 6 and 7 illustrate the jaw assembly 106 of the loading unit 100 in the open position with a pre-fired or unused cartridge assembly 116 received within the channel member 118. When the jaw assembly 106 is in the open position, regardless of the presence of a cartridge assembly 116 in the channel member 118, the biasing member 230 urges the firing lockout assembly 140 to the locked position. In this manner, the blocking portion 202 of the latch member 200 is in alignment with the stop surface 133 of the body 134 of the drive assembly 130, thereby preventing significant advancement of the drive assembly 130, i.e., beyond the initial advanced position. As shown in FIG. 7, the stop surface 133 of the drive assembly 130 is longitudinally spaced from the blocking portion 202 of the latch member 200 to permit the initial movement of the drive assembly 130 from a fully retracted position to the initial advanced position to allow the drive assembly 130 to cam the jaw assembly 106 to the approximated position. Similarly, the actuation sled 162 of the stapling assembly 160 is longitudinally spaced from the dynamic clamping member 132 of the drive assembly 130 to accommodate the initial advancement of the drive assembly 130 to allow for movement of the jaw assembly 106 to the approximated position.

When a pre-fired cartridge assembly 116 is received within the channel member 118 of the jaw assembly 106, the actuation sled 162 of the cartridge assembly 116 is in a proximal-most or fully retracted position. As noted above, in a pre-fired position with the dynamic clamping member 132 in its fully retracted position, the actuation sled 162 is longitudinally spaced from the dynamic clamping member 132 of the drive assembly 130. This arrangement permits initial advancement of the drive assembly 130 to cause the closing of the jaw assembly 106 without advancing the actuation sled 162. The extension 210 of the latch member 200 at least aligns with, if not engages, the engagement feature 162 a of the actuation sled 162.

FIGS. 8 and 9 illustrate the jaw assembly 106 of the tool assembly 104 of the loading unit 100 in the approximated position. As noted above, the jaw assembly 106 is moved to the approximated position, as indicated by arrow “A” in FIG. 8, through initial advancement of the dynamic clamping member 132 of the drive assembly 130 in the direction indicated by arrow “B” in FIG. 9. More particularly, advancement of the dynamic clamping member 132 of the drive assembly 130 in the direction of arrow “B” causes the upper flange 136 a of the dynamic clamping member 132 to engage the cam surface 153 of the anvil plate 152 and the lower flange 136 b of the dynamic clamping member 132 to engage the cam surface 131 of the channel member 118 to pivot the cartridge assembly 116 towards the anvil assembly 114 in the direction indicated by arrow “A”.

As the cartridge assembly 116 pivots relative to the anvil assembly 114 during initial advancement of the drive assembly 130, the latch member 200 of the firing lockout assembly 140 pivots against the urging of biasing member 230 (FIG. 5), as indicated by arrow “C” in FIG. 9, to the unlocked position. The latch member 200 is moved to the unlocked position through engagement of the extension 210 of the latch member 200 with the engagement feature 162 a of the actuation sled 162 of the cartridge assembly 116. Pivoting of the cartridge assembly 116 relative to the anvil assembly 114 causes corresponding pivoting of the latch member 200 relative to the drive assembly 130.

In the unlocked position, the blocking portion 202 of the latch member 200 is disposed out of alignment with the stop surface 133 of the drive assembly 130. As shown, the blocking portion 202 of the latch member 200 is disposed in alignment with the guide surface 135 of the drive assembly 130 to facilitate distal movement of the drive assembly 130 past the latch member 200.

FIG. 10 illustrates the loading unit 100 as the dynamic clamping member 132 is advanced to move the actuation sled 162 distally through the tool assembly 104. When the dynamic clamping 132 is advanced through the tool assembly 104 in the direction indicated by arrow “D”, the blocking portion 202 of the latch member 200 of the firing lockout assembly 140 engages the guide surface 135 of the drive assembly 130 to retain the latch member 200 in the unlocked position.

FIG. 11 illustrates the loading unit 100 as the drive assembly 130 is advanced in the direction indicated by arrow “E” to advance the actuation sled 162. As actuation sled 162 advances, staples “S” (FIG. 4) are ejected from the staple cartridge 156 of the cartridge assembly 116. Subsequent to advancement of the stop surface 133 of the drive assembly 130 past the blocking portion 202 of the latch member 200 of the firing lockout assembly 140, the latch member 200 is maintained in the unlocked position through engagement of the blocking portion 202 of the latch member 200 with an undersurface 134 a of the body 134 of the drive assembly 130.

FIG. 12 illustrates the loading unit 100 subsequent to firing of the cartridge assembly 116, and prior to the drive assembly 130 returning to a fully-retracted position. During retraction of the drive assembly 130, the latch member 200 of the firing lockout assembly 140 remains in the unlocked position through engagement of the blocking portion 202 of the latch member 200 with the undersurface 134 a of the body 134 of the drive assembly 130. Once the stop surface 133 of the drive assembly 130 is retracted beyond the blocking portion 202 of the latch member 200 and the dynamic clamping member 132 has moved proximally of the latch member 200, in the absence of the actuation sled 162 a of the cartridge assembly 116, the biasing member 230 of the firing lockout assembly 140 biases the latch member 200 to the locked position. In the locked position, the drive assembly 130 is prevented from advancing beyond the initial advanced position through engagement of the blocking portion 202 of the latch member 200 with the stop surface 133 of the drive assembly 130, thereby preventing further advancement of the drive assembly 130.

To reuse stapling device 10, the drive assembly 130 is fully retracted to cause the opening of the jaw assembly 106. When the dynamic clamping member 132 is in the fully retracted position, a biasing member (not shown) urges the jaw assembly 106 to the open position. The spent cartridge assembly is then removed from the channel member 118 and a new cartridge assembly 116 is positioned within the channel member 118. As the new cartridge assembly 116 includes an actuation sled 162 positioned such that an engagement feature 162 of the actuation sled 162 aligns with the extension 210 of the latch member 200 to cause the latch member 200 to move to the unlocked position when the drive assembly 130 is initially advanced to cause the closing of the jaw assembly 106, and the further firing of the stapling device 10.

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary aspects. It is envisioned that the elements and features illustrated or described in connection with the exemplary aspects may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described aspects. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

1. (canceled)
 2. A loading unit for a surgical stapling device, the loading unit comprising: a body portion defining a longitudinal axis having a proximal portion and a distal portion; a tool assembly supported on the distal portion of the body portion, the tool assembly including an anvil assembly and a channel member pivotally supported relative to the anvil assembly, the channel member being configured to releasably receive a cartridge assembly, the tool assembly being movable from an open condition to an approximated condition; a drive assembly supported within the tool assembly and movable from a retracted position to an initial advanced position to move the tool assembly from the open condition to the approximated condition, the drive assembly having a stop surface; and a firing lockout assembly including a latch member having a blocking portion, the latch member being pivotally supported within the tool assembly and movable between a first position and a second position, wherein in the first position the blocking portion of the latch member is aligned with the stop surface of the drive assembly to prevent advancement of the drive assembly within the tool assembly beyond the initial advanced position and in the second position the blocking portion is misaligned with the stop surface of the drive assembly to permit advancement of the drive assembly within the tool assembly beyond the initial advanced position, wherein the latch member remains in the first position as the tool assembly moves to the approximated condition in an absence of a cartridge assembly having an actuation sled in a sled retracted position received within the channel member.
 3. The loading unit of claim 2, further including a cartridge assembly received within the channel member, the cartridge assembly including an actuation sled, the actuation sled positioned within the cartridge assembly to be engaged by the drive assembly and movable from a sled retracted position to a sled advanced position.
 4. The loading unit of claim 3, wherein the drive assembly is movable from the initial advanced position to a fully advanced position to effect movement of the actuation sled from the sled retracted position to the sled advanced position.
 5. The loading unit of claim 3, wherein the firing lockout assembly further includes a biasing member, the biasing member being positioned to urge the latch member towards the first position
 6. The loading unit of claim 5, wherein the actuation sled includes an engagement feature, the engagement feature engaging the latch member to move the latch member from the first position to the second position when the tool assembly is moved to the approximated condition and the actuation sled is in the sled retracted position.
 7. The loading unit of claim 6, wherein the latch member includes first and second legs extending distally from the blocking portion, each of the first and second legs supporting a pivot member.
 8. The loading unit of claim 7, wherein the latch member includes an extension extending from one of the first or second legs, the extension engaging the engagement feature to move the latch member to the second position when the tool assembly is moved to the approximated condition.
 9. The loading unit of claim 3, wherein movement of the drive assembly beyond the initial advanced position moves the actuation sled from the sled retracted position towards the sled advanced position to eject a plurality of staples from the cartridge assembly.
 10. The loading unit of claim 4, wherein the drive assembly includes a body and a clamping member having an upper flange and a lower flange interconnected by a vertical strut, the clamping member being positioned to engage the actuation sled to move the actuation sled distally within the cartridge assembly as the drive assembly moves from the initial advanced position towards the fully advanced position.
 11. The loading unit of claim 10, wherein the body of the drive assembly includes the stop surface.
 12. The loading unit of claim 11, wherein the body of the drive assembly includes a guide surface positioned to retain the latch member in the second position.
 13. The loading unit of claim 10, wherein the anvil assembly defines a first cam surface and the cartridge assembly defines a second cam surface, the upper and lower flanges of the clamping member of the drive assembly engaging the first and second cam surfaces as the drive assembly moves from the retracted position to the initial advanced position to move the tool assembly to the approximated condition.
 14. The loading unit of claim 13, wherein the blocking portion of the latch member is positioned to engage a bottom surface of the body of the drive assembly as the drive assembly is moved from the initial advanced position towards the fully advanced position to retain the latch member in the second position.
 15. The loading unit of claim 13, wherein the actuation sled is in abutting relationship with the clamping member of the drive assembly such that upon movement of the drive assembly from the fully advanced position back towards the retracted position, the actuation sled remains in the sled advanced position.
 16. A surgical stapling device comprising: a body portion defining a longitudinal axis having a proximal portion and a distal portion; a tool assembly supported on the distal portion of the body portion, the tool assembly including an anvil assembly and a channel member pivotally supported relative to the anvil assembly, the channel member being configured to releasably receive a cartridge assembly, the tool assembly being movable from an open condition to an approximated condition; a drive assembly supported within the tool assembly and movable from a retracted position to an initial advanced position to move the tool assembly from the open condition to the approximated condition, the drive assembly having a stop surface; and a firing lockout assembly including a latch member and a biasing member, the latch member having a blocking portion and being pivotally supported within the tool assembly between a first position and a second position, the biasing member being configured to urge the latch member to the first position, wherein in the first position, the blocking portion of the latch member is aligned with the stop surface of the drive assembly to prevent advancement of the drive assembly within the tool assembly beyond the initial advanced position and in the second position the blocking portion is misaligned with the stop surface of the drive assembly to permit advancement of the drive assembly within the tool assembly beyond the initial advanced position, wherein the latch member remains in the first position as the tool assembly moves to the approximated condition in an absence of a cartridge assembly having an actuation sled in a fully retracted position being received within the channel member.
 17. The surgical stapling device of claim 16, further including a cartridge assembly received within the channel member, the cartridge assembly including an actuation sled, wherein the actuation sled is positioned within the cartridge assembly to be engaged by the drive assembly subsequent to the drive assembly moving to the initial advanced position.
 18. The surgical stapling device of claim 17, wherein the drive assembly is movable from the initial advanced position to a fully advanced position to effect movement of the actuation sled from the sled retracted position to the sled advanced position.
 19. The surgical stapling device of claim 18, wherein the actuation sled includes an engagement feature, the engagement feature engaging the latch member to move the latch member from the first position to the second position when tool assembly is moved to the approximated condition and the actuation sled is in the sled retracted position.
 20. The surgical stapling device of claim 19, wherein the latch member includes first and second legs extending distally from the blocking portion, each of the first and second legs supporting a pivot member.
 21. A surgical stapling device comprising: a handle assembly; and a loading unit releasably secured to the handle assembly, the loading unit including, a body portion defining a longitudinal axis having a proximal portion and a distal portion; a tool assembly supported on the distal portion of the body portion, the tool assembly including an anvil assembly and a channel member pivotally supported relative to the anvil assembly, the channel member being configured to releasably receive a cartridge assembly, the tool assembly being movable from an open condition to an approximated condition; a drive assembly supported within the tool assembly and movable from a retracted position to an initial advanced position to move the tool assembly from the open condition to the approximated condition, the drive assembly having a stop surface; and a firing lockout assembly including a latch member and a biasing member, the latch member having a blocking portion and being pivotally supported within the tool assembly between a first position to a second position, the biasing member being configured to urge the latch member to the first position, wherein in the first position, the blocking portion of the latch member is aligned with the stop surface of the drive assembly to prevent advancement of the drive assembly within the tool assembly beyond the initial advanced position and in the second position the blocking portion is misaligned with the stop surface of the drive assembly to permit advancement of the drive assembly within the tool assembly beyond the initial advanced position, wherein the latch member remains in the first position as the tool assembly moves to the approximated condition in an absence of a cartridge assembly having an actuation sled in a fully retracted position being received within the channel member. 